package com.winhxd.b2c.gateway.config;

import com.winhxd.b2c.common.context.support.ContextHelper;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.HttpStatus;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.util.CollectionUtils;
import org.springframework.web.cors.reactive.CorsUtils;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebFilter;
import org.springframework.web.server.WebFilterChain;
import reactor.core.publisher.Mono;

import java.util.List;

/**
 * Web请求跨域支持
 *
 * @author lixiaodong
 */
@Configuration
public class CorsConfig {
    private static final String ALLOWED_HEADERS = "*";
    private static final String ALLOWED_METHODS = "*";
    private static final String ALLOWED_ORIGIN = "*";
    private static final String ALLOWED_EXPOSE = ContextHelper.TRACER_API_TRACE_ID;
    private static final String MAX_AGE = "864000";

    @Bean
    public WebFilter corsFilter() {
        return (ServerWebExchange ctx, WebFilterChain chain) -> {
            ServerHttpRequest request = ctx.getRequest();
            if (CorsUtils.isCorsRequest(request)) {
                List<String> accessControlRequestHeaders = request.getHeaders().getAccessControlRequestHeaders();
                ServerHttpResponse response = ctx.getResponse();
                HttpHeaders headers = response.getHeaders();
                headers.add("Access-Control-Allow-Origin", ALLOWED_ORIGIN);
                headers.add("Access-Control-Allow-Methods", ALLOWED_METHODS);
                headers.add("Access-Control-Max-Age", MAX_AGE);
                if (CollectionUtils.isEmpty(accessControlRequestHeaders)) {
                    headers.add("Access-Control-Allow-Headers", ALLOWED_HEADERS);
                } else {
                    headers.add("Access-Control-Allow-Headers",
                            String.join(",", accessControlRequestHeaders));
                }
                headers.add("Access-Control-Expose-Headers", ALLOWED_EXPOSE);
                headers.add("Access-Control-Allow-Credentials", "true");
                if (request.getMethod() == HttpMethod.OPTIONS) {
                    response.setStatusCode(HttpStatus.OK);
                    return Mono.empty();
                }
            }
            return chain.filter(ctx);
        };
    }
}